We have developed a new method for the quantiative autoradiography of synaptic components. Frozen brain slices are incubated in vitro with tritiated ligands to label neurotransmitter receptors or presynaptic uptake sites. The labeled brain slices are placed against tritium-sensitive sheet film (LKB Ultrofilm) to generate autoradiograms. The resulting autoradiogram is a quantitative representation of the synaptic component, and can be analyzed by computerized methods of densitometry. We will use computerized densitometry to make detailed saturation and kinetic studies of receptors in microregions of rat brain. Neurotransmitter receptors will be quantified in hippocampal subregions of rat brain after exposure to the steroid hormone, corticosterone. Presynaptic uptake sites for monoamine neurotransmitters will be measured in rat brain, and correlated with the known distribution of monoamine terminals. The receptors for the neurotransmitter glutamate will be quantified by computerized methods of autoradiography. The goal of our research is to develop computerized methods to measure synaptic molecules in micro-sized regions of the brain. New methods of neurochemistry are necessary ot elucidate the basis of neurological and psychiatric diseases which result from biochemical defects in small regions of the brain.